Android 6.1 update z4 tablet not showing in windows 10

Hi, on android 6.0, plug tablet into pc, on tablet screen usual options apply ( MTP, charge olny etc), now, on android 6.1, no opions show on tablet, pc makes a ding noise to acknowledge tablet is conected, but its not showing in file explorer, and my tablet only gives me this message now "usb : use dedicated charger t charge tablet". ive clicked connection options, nothing in there seems to enable file transfer, what the hell has happened between 6.0 and 6.1 to stop this simple feature from working. I've tried multiple usb cables too, nothing changes, and there have been zero changes to my pc. Anyone else seen this last few days since update...

thanks

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